Silver halide photographic light-sensitive elements are normally stored before use in a closed moistureproof vessel. For example, silver halide photographic color elements are most often enclosed in light-tight cartridges, such as 135, 110 and 120 cartridges; said cartridges including the light-sensitive element are sealed in a closed, air-tight vessel to protect the light-sensitive element against degradation of photographic properties caused by external moisture or noxious gases and stored therein before use in photographic cameras. Other examples include photographic elements in the form of sheets, bands or industrial coatings which are stored in closed vessels before use or converting and wherein the internal volume in the closed vessel is very low compared with the surface area of the photographic element.
A problem has been observed of uniform fog occurring in photographic elements sealed in closed vessels. This has been observed in particular with photographic elements containing silver halide emulsion layers which have been sensitised with sulfur and gold.
U.S. Pat. Nos. 4,892,808, 4,211,837 and 3,900,323 disclose that said uniform fog can be reduced by the use of heavy metal compounds capable of scavenging noxious substances produced by carbon black used in the opaque backing sheet placed on the side of the photographic element opposite the side bearing the silver halide emulsion layers. According to U.S. Pat No. 4,892,808 said fog is caused by hydrogen cyanide (HCN) gas which evolves from the carbon black of the associated backing material and binds with gold in sulfur and gold sensitized silver halide grains, thus leaving silver sulfide fog centers. Examples of heavy metal compounds include compounds of palladium, gold, platinum, iridium, rhodium and osmium.
JP-A-62-168143 discloses that fog occurring in a light-sensitive element during storage in a closed vessel can be reduced by decreasing the humidity in the vessel. However, when humidity is decreased to a value at which fog is satisfactory reduced, problems of static failure, low curling and fragility can occur.
EP 439,069 discloses that fog in photographic elements, containing silver halide emulsion layers sensitised with sulfur and gold, stored in a closed vessel can be caused by a noxious gas released from said photographic element. On the basis of their experiments, the inventors of EP 439,069 have found that HCN was the gas released from the photographic element and accumulated in the closed vessel to undesirably change photographic properties. According to their experiments, synthetic polymers (e.g., couplers, matting agents, binders) synthesized by an azo-based polymerization initiator containing a cyano group, ultraviolet absorbers containing a cyano group, or dyes containing a cyano group have been found to be the source of HCN gas production and removing this cause was a most preferably means in order to suppress releasing of HCN gas from the photographic element.
JP-A-03-236043, JP-A-03-236044, JP-A-03-236048, JP-A-03-236049 and JP-A-03-236050 all relate to means for reducing deterioration of photographic characteristics caused by HCN gas released by keeping a photographic element comprising silver halide emulsion layers sensitised with sulfur and gold in an air-tight vessel able to keep fixed humidity.
The present invention is based on the discovery of an additional source of HCN gas in photographic elements stored in a closed vessel. It has been found that fog in silver halide photographic elements stored in closed vessel is mainly caused by HCN gas released by chlorinated s-triazine compounds used as hardeners for the hydrophilic binders (such as gelatin) of the element. It is believed that HCN is produced during the hydrolisis of cyanuric chloride used as starting material for the synthesis of chlorinated s-triazine hardeners. The fact that the source of HCN gas released from a light-sensitive element can be a chlorinated s-triazine hardener was very surprising, since it is not known in the art.
Both photographically useful chemical compounds comprising cyano groups, such as those described in EP 439,069, and chlorinated s-triazine hardeners are compounds widely used in silver halide color photographic elements and substituting them to suppress releasing of HCN gas from the element may cause problems as far as other photographic performances of the element are concerned. Accordingly, it is an object of the present invention to provide silver halide photographic elements in which fog formation is small when the element is stored in a closed vessel without removing the above compounds from the element.
U.S. Pat. Nos. 2,566,245 and 2,566,263 describe certain heavy metal compounds as fog-inhibitors for silver halide emulsions to improve keeping under high humidity and high temperature conditions, as in tropical regions. There is no suggestion in these patents that fog is caused by HCN released from a photographic element sealed in a closed vessel. EP 439,069, cited above, states that serious problems of degradation in photographic properties arise when heavy metal compounds are added to the light-sensitive element. U.S. Pat. No. 4,892,808, cited above, suggests that the heavy metal compound be placed in a location remote from the silver halide emulsion layer. U.S. Pat. No. 2,472,631 discloses fogging properties of cyano palladite anions (which anions should be formed by the reaction of palladium compouds with HCN).